Obesity among youth tripled in the United States from 1980 to 2000 despite numerous public health interventions designed to educate youth about the benefits of a healthy diet and physical activity. After witnessing the success of public policy adoption targeting other public health issues (e.g. tobacco, bike helmets, seat belts) obesity researchers and policymakers have promoted policy as an intervention tool. The number of state bills and resolutions targeting youth obesity increased substantially in the past decade;however, very little is known about whether these policies have an effect on diet, activity, or BMI. A recent report from NHANES showed that there was no significant increase in average national prevalence of youth obesity between 1999 and 2006. This absence of change, after decades of consistent increases, suggests that policies implemented in the past decade could be having a positive effect. In this research we will use multi-level modeling to examine trends in BMI and weight-related behaviors in high school students within and across states. We will then examine associations between study state level policies for high schools and BMI and weight-related behaviors. Data for this work will be from the Youth Risk Behavior Surveillance (YRBS) and the School Health Programs and Policies Study (SHPPS). The Aims of the research are: Aim 1: To examine between-state differences in youth BMI time trends from 2001-07 and identify demographic and behavioral variables that contribute to the heterogeneity. Aim 2: To estimate the proportion of within-state changes in youth BMI from 2001-07 that is associated with demographic and behavioral changes. Aim 3: To determine if changes in state-level nutrition and physical activity policies from 2000-06 are associated with youth nutrition and physical activity behaviors in 2007. Aim 4: To determine if changes in state-level nutrition and physical activity related policies from 2000-06 are associated with youth BMI and obesity prevalence in 2007. Given the enormity of the destructive effects of the obesity epidemic on the current and future health of American youth, it is surprising that so little work has been done to evaluate the effects of large scale policies. To our knowledge, this will be the first study to merge data from the YRBS to that from SHPPS to estimate the impact of state-level policies on weight-related behaviors and obesity in youth. PUBLIC HEALTH RELEVANCE: We will study state policies effecting high schools to estimate their effects on adolescent behavior and BMI. This will be the most comprehensive study on this topic to date and will advance the field of obesity policy research;a field that has strong potential to impact the health of our youth, but has only just begun.